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    Re: mirror horizon
    From: Bill Morris
    Date: 2011 Mar 23, 19:02 -0700


    Use only three screws, two along one side and the other in the middle of the opposite side. Place the level on the mirror parallel to the line of the first two screws and level. Then place it at right angles to that line and level with the third screw. Repeat as a check. Provided the pitch of the screws is reasonably fine, this should take no more than two minutes. However, if you take it outside and set it up on a rough concrete surface, rotating the screws will tend to make your breadboard move about, affecting the level, so as an improvisation, I suggest you Araldite three small white metal American coins to your chosen site and surround them with large washers that are rather thicker than the coins and just fit around them.

    A layer of felt between the mirror and the board would be a good idea to take up any irregularities, and make sure that there is free movement of the mirror on the board. The transparent pieces of plastic you are using should not press directly on the mirror, i.e. use them to locate but not to fasten the mirror, or you will introduce distortions.

    Bill (noone-calls-me-William) Morris
    New Zealand
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